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Proceedings of 8th NEAJ Symposium on Current and Future Technologies Edited by: Dr. Binaya Kumar Mishra, Dr. Ram Krishna Regmi & Dr.
Badri Bhakta Shrestha
8th NEAJ Symposium on Current and Future Technologies
25 January 2015, Tokyo, Japan
8th
Nepalese Engineers Association, Japan (NEAJ)
Proceedings of 8th
NEAJ Symposium on Current and Future
Technologies
8th NEAJ Symposium on Current and Future Technologies: Organized by Nepalese
Engineers Association Japan (NEAJ)
25 January 2015, Hongo Campus, The University of Tokyo, Tokyo, Japan
Edited by:
Dr. Binaya Kumar Mishra1, Dr. Ram Krishna Regmi
1 & Dr. Badri Bhakta
Shrestha2
1United Nations University, Tokyo, Japan
2International Centre for Water Hazard and Risk Management, Public Works Research
Institute, Tsukuba, Japan
Organizing Committee:
Chairperson
Er. Dr. Binaya Kumar Mishra, United Nations University
Technical Committee Er. Dr. Achyut Sapkota, Chiba University
Er. Dr. Bhoj Raj Pantha, KEI Consultants
Er. Dr. Maheswor Shrestha, The University of Tokyo
Er. Pawan Kumar Bhattarai, Kyoto University
Er. Dr. Ram Krishna Regmi, United Nations University
Er. Dr. Ved Prasad Kafle, National Institute of Information and Communication Technology
Local Organizing Committee Er. Amit Regmi, E &T Japan Co. Ltd
Er. Khagendra Belbase, Tokyo Institute of Technology
Er. Dr. Ram Krishna Regmi, United Nations University
Er. Sapana Poudel, The University of Tokyo
Table of Contents
1. INTRODUCTION TO 5TH GENERATION MOBILE COMMUNICATION NETWORKS
- Ved Prasad KAFLE ………………………………………………………………………1
2. INTRNET OF THINGS (IOT) - Chandi Prasad SUBEDI ………………………………….2
3. ENGINEERING IN MEDICINE AND BIOLOGY - Achyut SAPKOTA …………………..3
4. DO ACCESS TO TECHNOLOGY, MEDIA AND PRIVATE TUTION IMPROVE
STUDENTS TEST SCORES? A GENDER AND CAST BASED EVIDENCE FROM
SCHOOL LEAVING CERTIFICATE (SLC) EXAM IN NEPAL - Nirmal Kumar RAUT
………………………………………………………………………………………………..4
5. UTILIZATION OF COMMUNAL SPACES IN HISTORIC CITY PATAN AFTER 1934
THE GREAT EARTHQUAKE - Lata SHAKYA, Takeyuki OKUBO ……………………......6
6. LARGE-SCALE LANDSLIDES IN THE NEPAL HIMALAYAS AND LESSONS
LEARNT FROM THE JURE LANDSLIDE EVENT FOR LANDSLIDE HAZARD
MANAGEMENT PRACTICE IN THE COUNTRY - Netra Prakash BHANDARY ……....8
7. SOFT ROCK SLOPE WEATHERING DUE TO RAINWATER - Manita NAKARMI …....9
8. COUPLING RATIO OF COUPLED SHEAR WALLS - Rohit Kumar ADHIKARI, Anil C.
WIJEYEWICKREMA ………………………………………………………………..……...10
9. DETERMINATION OF WATER QUALITY INDEX OF BAGMATI RIVER - Ram
Krishna REGMI, Binaya Kumar MISHRA, Pingping LUO, Asako TOYOZUMI-KOJIMA,
Kensuke FUKUSHI, Kazuhiko TAKEMOTO ……………………………………………....12
10. DEVELOPMENT OF METHODOLOGY FOR LANDSLIDE AND DEBRIS FLOW
FORECASTING SYSTEM - Badri Bhakta SHRESTHA ……………………….…………13
11. EXPERIMENTAL EVIDENCE OF IMPACT OF FLOW DIRECTION ON DYKE
BREACH CHARACTERISTICS DUE TO FLOW OVERTOPPING - Pawan Kumar
BHATTARAI, Hajime NAKAGAWA, Kenji KAWAIKE, Hao ZHANG ………………….....15
1
8th
NEAJ Symposium on Current and Future Technologies
Tokyo, Japan January 25, 2015
INTRODUCTION TO 5TH GENERATION MOBILE
COMMUNICATION NETWORKS
Ved Prasad KAFLE*1
1 National Institute of Information and communications
*Email: [email protected]
Abstract Research and experiments have recently begun to develop the next generation mobile
communication networks, which are also referred to as the fifth generation (5G) wireless
communication systems. 5G communication networks are targeted at commercial deployment in
2020 or beyond. They are expected to enable ultra-high-speed data transmission (>10Gbps) that
would be about 1000 times the speed of current LTE (i.e. 4G) networks, connect massive number
of devices (>50 billion) that would be 10-100 times the number of existing mobile phones, 10 times
longer battery life, and 5 times reduced end-to-end latency. Not only the mobile phones and
computers but also machines, home appliances, vehicles, sensors, etc. get connected to the 5G
systems for enabling Machine-to-Machine (M2M) communications required for realizing the future
network society. As the components of 5G wireless communication systems, various technologies
such as utilization of new frequency spectrum (e.g. millimeter bands), cognitive radio, ultradense
cell deployment, coexistence of heterogeneous access networks, infrastructure virtualization,
software-defined networking (SDN), and device-to-device (D2D) communications are being
studied. In the presentation I will summarised some of the recent research activities on the 5G
network development.
2
8th
NEAJ Symposium on Current and Future Technologies
Tokyo, Japan January 25, 2015
INTRNET OF THINGS (IOT)
Chandi Prasad SUBEDI*1
1 Softbank Corporation
*Email: [email protected]
Abstract Internet of Things simply implies of the living or simply a thing that is connected to the internet
world. The concept is not new but due to advent of IPv6 and low cost computing platform together
with low powered radio technology, things connected to the Internet building a paradigm shift to
the next generation information technology.
In this presentation , Er. Subedi will try to show the examples how IoT is evolving , its challenges
and how the technology will affect our daily life in next few decades and how the technology will
be helpful to the developing country like Nepal.
3
8th
NEAJ Symposium on Current and Future Technologies
Tokyo, Japan January 25, 2015
ENGINEERING IN MEDICINE AND BIOLOGY
Achyut SAPKOTA*1
1 Graduate School of Engineering, Chiba University
*Email: [email protected]
Abstract General overview of medical and biological applications of engineering will be discussed.
Discussions will be based on speaker’s past and current research projects, viz.: i) computational
prediction of the bimolecular networks in rice (as a model organism for cereal biology), ii) risk
analysis and detection of blood clot in extracorporeal circulation systems (eg. hemodialyzer,
cardiopulmonary bypass, ventricular assistance devices etc) by exploiting the electrical properties
of blood and iii) biological cell manipulations using various electro-mechanical forces.
4
8th
NEAJ Symposium on Current and Future Technologies
Tokyo, Japan January 25, 2015
DO ACCESS TO TECHNOLOGY, MEDIA AND PRIVATE TUTION
IMPROVE STUDENTS TEST SCORES? A GENDER AND CAST
BASED EVIDENCE FROM SCHOOL LEAVING CERTIFICATE
(SLC) EXAM IN NEPAL
Nirmal Kumar RAUT*1
1 Graduate Student, National Graduate Institute for Policy Studies (GRISP), Tokyo
*Email: [email protected]
Keywords: School Leaving Certificate, Test Scores
Background The School Leaving Certificate examinations (SLC) is the final examination in the secondary
school systems of Nepal. It is considered as a "iron gate" for its importance to open up future
avenues for the candidates so far as choice of discipline and career choice are concerned.
Issues for Nepal : SLC failures occur primarily in compulsory subjects like Math, Science and
English and this is more problematic in girls and non-high caste candidates often leading to
serious social problems such as depression and suicides. Facts: (1)Test scores of female
candidates in SLC are significantly lower than female. (2)Access to technology and media
such as computer, email, internet, television, newspaper at home is constrained more in case of
female than male. (3)Access to technology and media such as computer, email, internet,
television and newspaper at home is constrained more in case of low caste households than
high caste households (See Tables in the slides)
Approach Hypotheses:
H1: Has additional investment on education (Private tuition) helped improve the Test Scores?
H2: Do access to technology and media help improve the test scores?
H3: Who benefits more from Private tuition, technology and media?
• Male or Female;
• High Caste or Low Caste
Data and Methods: Repeated Cross Section (2002, 2003 and 2004) of Comprehensive SLC Survey
Data set collected in 2005 by Ministry of Education, Nepal
• Econometric Model - Fixed Effect OLS Model:
Where Y is the SLC test score
X is the student Characteristics
F is family Characteristics
α is the School Fixed Effect
t is the time fixed effect
Є is the random error term clustered at school level
i is student, s is school and t is time period Note: I believe that the unobserved heterogeneity of a child to some extent will be taken care by the variable "Family Members passing SLC " if we assume that the ability is hereditary. Furthermore, I admit that the endogeneity issue primarily from reverse causality
may yet remain which will be addressed in the final version of this paper using proper instrumentation.
isttsististist tFXY ''
5
Results/Findings Private tuition does not improve the test score of male. Female reap more benefit. Computer, email
and television plays a significant role in increasing the test scores in general. High caste candidates
benefit more from email and newspaper whereas low caste candidates benefit more from computer
and television. Private tuition, email and television help improve English score whereas computer
helps improving both math and science test scores Female candidates increase English and Science
test scores with computer at home whereas private tuition increase their Math and Science score.
High caste candidate do not benefit from television at home since they lower their math and science
score.
Policy Implication: A substitution to an ICT based education rather than on the stereotype tuition
system that emphasizes rote learning. More human capital investment on female candidates with
private tuition and access to technology through subsidized tuition fee. Poor and low caste
candidates can access to computer only if the state subsidizes their purchase of computer.
Table 1: Fixed Effect OLS Model ( Only impact on overall SLC test score reported in this
Table)
References
Casey, A., R. Layte, , S. Lyons & M. Silles: Home computer use and academic performance of
9-year-olds, Oxford Review of Education 38 (5), 2012, pp.617-634
Dang, H., Rogers, F.H.: How to interpret the growing phenomenon of private tutoring:
human capital deepening, inequality increasing, or waste of resources?, Policy Research Working
Paper Series of The World Bank, 2008, No. 4530
Mischo, C., & Haag, L.: Expansion and effectiveness of private tutoring. European Journal of
Psychology of Education, 17(3), 2002, pp.263-273
Zhang, Y. : Does private tutoring improve students’ National College Entrance Examination
performance? – A case study from Jinan, China. Economics of Education Review, 32, 2013c, pp.1-2
6
8th
NEAJ Symposium on Current and Future Technologies
Tokyo, Japan January 25, 2015
UTILIZATION OF COMMUNAL SPACES IN HISTORIC CITY
PATAN AFTER 1934 THE GREAT EARTHQUAKE
Lata SHAKYA*1, Takeyuki OKUBO
2
1 JSPS Postdoctoral Fellow, Department of Architecture, University of Tokyo
2 Department of Science and Engineering, Ritsumeikan University
*Email: [email protected]
Keywords: 1934 the great earthquake 1934, courtyard, rest house, shelter, Nepal
Background
Nepal has experienced many destructive earthquakes. A 1934 AD earthquake is one of the
largest earthquakes in Nepal which destroyed 20 percent and damaged 40 percent of the
valley’s building in Kathmandu valley. The seismic record of the region suggests that
earthquake of this size occurs approximately every 75 years, and is likely to occur in the
near future1.
Ministry of Home, Ministry of Housing and Physical Planning, Department of Mines and
Geology are the main government institutions involving for the earthquake risk
management. Ministry of Housing and Physical Planning has implemented projects for the
rehabilitation and reconstruction of earthquake damaged buildings, and also has
formulated the national building code. In non-governmental institutions, NSET (National
Society for Earthquake Technology-Nepal) and JICA are the few of the institutions,
working for earthquake risk management. Although the simulation work related
earthquake disaster by governmental and non-governmental section has been continuing,
there are still lack of actual data related to life environment and recovery process story of
past earthquakes.
In this paper, utilization of communal spaces and life environment after 1934 the great
earthquake in historic city Patan is clarified through literature review and interview survey
with the great earthquake experienced elderly people living in historic city Patan.
Approach There exist only one book named “Nepalko Mahabhukampa 1990 saal” published in next year of
the earthquake which has recorded the situation of all over the country including Kathmandu
valley. The issues related with shelter inside the valley and immediate actions of government after
the earthquake is extracted from this book as literature review.
Interview survey was conducted with four elderly persons who have experienced 1934 the great
earthquake. The location of elderly persons’ living place is shown in figure 1, which are Nagbahal
tole, Ikhachhen tole and its surrounding area. Elderly from the localized area in the vicinity of
Nagbahal area was selected so that the features of the specific space soon after 1934 the great
earthquake could be clarified.
7
Fig1. Living place of the elderly who have experienced the great earthquake 1934
Results/Findings
Fig2. Life environment of four elderly after 1934 the great earthquake
From figure 2, it can be clarified that communal spaces like courtyard, rest houses
(Phalcha) were used as shelter. In addition, community house owned by Sangha
(management organization of Buddhist monastery) was also used as shelter.
It is verified that people chose places for shelter nearby their properties so that they can
take care of property as well as they can live together with their community. This fact
provides an important hint for planning shelters and temporary housing for earthquake
victims in case of devastating earthquake in future.
References:
1) NSET & Geo Hazards International (GHI)(1999):The Kathmandu Valley Earthquake Risk Management
Action Plan
2) NSET&GHI (1999): Kathmandu Valley’s Earthquake Scenario. NSET, Kathmandu
3) Kathmandu Valley Earthquake Risk Management Project (2002): Project Completion Report, under the Asian
Urban Disaster Mitigation Program, Asian Disaster Preparedness Center, Bangkok, Thailand
4) JICA(2002):The study on Earthquake Disaster Mitigation, In the Kathmandu Valley, Kingdom of Nepal, final
report
5) Bramhasamshera Jangabahadura rana (1935) : Nepalako mahabhukampa, 1990 sala
8
8th
NEAJ Symposium on Current and Future Technologies
Tokyo, Japan January 25, 2015
LARGE-SCALE LANDSLIDES IN THE NEPAL HIMALAYAS AND
LESSONS LEARNT FROM THE JURE LANDSLIDE EVENT FOR
LANDSLIDE HAZARD MANAGEMENT PRACTICE IN THE
COUNTRY
Netra Prakash BHANDARY*
1
1 Graduate School of Science and Engineering, Ehime University
*E-mail: [email protected] Abstract The main and the core natural cause of large-scale landslide occurrences in the Nepal Himalayas is
ever continuing mountain building process due to plate collision aided by heavy amount of
precipitation and seismic activities. At the same time, uncontrolled human activities that mainly
include settlement expansions and infrastructure developments have largely accelerated the land
sliding process recently, and have resulted in massive loss of life and individual as well as public
properties. However, the nation still lacks an effective disaster prevention law and people do not have
adequate knowledge about staying safe from natural hazards and dealing with post-disaster situation.
The government also does not have specific goals or plans to manage natural hazards and prevent
disasters. Recent landslide and flood disasters all over the nation and the government’s efforts to deal
with the post-disaster scenario and chaos are evident that we still have a long way to go to have an
effective hazard management plan. Most of our national roads pass through large-scale landslide
slopes while the preventive measures we have applied at the roadsides are very traditional and
ineffective such as gabion walls at extremely failure-prone areas. We do not even have an up-to-date
map of existing landslides on roadsides as well as human settlements. We have never thought of the
landslide safety of our people that are option-less and are compelled to live on landslide masses in
remote mountain areas. We have never thought of the safety of fellow citizens that live on the
flood-prone river banks. Our government officials together with the land brokers rather promote an
unhealthy land business and develop riverbanks into newer urban settlements risking the dwellers’
life. All these human activities have largely increased the disaster risk level in Nepal. In fact, as a
mountainous country, Nepal does have a dense distribution of large-scale landslides that may or may
not be in active state of sliding but our activities promote their reactivation. Despite our knowledge
that the recent Jure landslide was in active state, we could do nothing before as well as after the
landslide event of August this year. There are many locations in our national roads that have
Jure-type landslide hazards, and learning from the chaos we had during the Jure landslide disaster,
we urgently need to enact a truly scientific hazard management and disaster mitigation law. This
presentation includes landslide occurrence scenario, large-scale landslide hazard, their scientific,
engineering, and social importance, Jure landslide and landslide dam formation, its economic impact,
government’s response, and similar issues.
9
8th
NEAJ Symposium on Current and Future Technologies
Tokyo, Japan January 25, 2015
SOFT ROCK SLOPE WEATHERING DUE TO RAINWATER
Manita NAKARMI*
1
1 The University of Tokyo
*E-mail: [email protected]
Abstract
Nepal is a mountainous country. The summer monsoon season in Nepal covers about 75% of
annual precipitation from June to September, triggering many landslides. It rains almost
every day resulting in a hot and wet weather which is a favorable environment for chemical
weathering. The clear rainwater is slightly acidic in nature with PH-value ranging from 5 to
5.6 due to the presence of CO2 in air. In rainwater, some rock minerals simply dissolves or
some reacts with acid content of rainwater and the rock slope weathers. The simulation of
such weathering process is being studied in this research work. The relationship between
shear strength and shear wave velocity is developed for artificial sandstone made from silica
sand, gypsum and CaCO3. From this relationship, the negative ageing of the geo-material is
easily understood. In addition, with field measured shear wave velocity, the shear strength of
the slope is also determined. The weathering process is conducted in three cases 1) water
only, 2) water with PH-5, 3) water with PH-4. For the first two cases, there is not much
difference in the weathering trend. But with the solution of PH- 4, the weathering of the rock
sample is relatively fast and the strength loss of sample is comparatively more.
Keywords: Rock weathering, chemical weathering, rainwater, PH, shear strength, shear
wave velocity, negative ageing.
10
8th
NEAJ Symposium on Current and Future Technologies
Tokyo, Japan January 25, 2015
COUPLING RATIO OF COUPLED SHEAR WALLS
Rohit Kumar ADHIKARI*
1, Anil C. WIJEYEWICKREMA
2
1, 2
Department of Civil Engineering, Tokyo Institute of Technology
*E-mail: [email protected]
Keywords: Coupled shear wall, Displacement based design, Coupling ratio, Non-linear time
history analysis
Background Coupled RC shear walls are efficient structural systems for resisting wind and seismic forces in
multi-story buildings. This is due to the fact that, besides walls, coupling beams also take part in
dissipating seismic energy through the formation of plastic
hinges at two ends. The openings required in the buildings for
lifts, doors, windows etc. also sometimes necessitate the use of
coupled shear walls. The ratio of moment resisted by the
coupling action to the total overturning moment is defined as the
coupling ratio ( β ). Coupling ratio is one of the important
parameters in the design of coupled walls (Priestley et al.,
2007). If this ratio is very small, the walls behave only as
connected walls and if too large, the coupled wall behaves as a
single cantilever wall. During the initial phase of design, based
on the expected energy dissipation mechanism and behavior of
coupled wall system, an appropriate value (usually 0.25 to 0.6)
of this ratio is assumed. If the actual coupling ratio during real
earthquake scenario is different from the initially assumed one,
then the behavior of coupled wall system is significantly
different from what is expected.
So, in this study, a comparison is made between the initially
assumed and actual coupling ratio during real earthquakes for a
number of coupled wall systems with varying heights and
coupling ratios. Fig. 1.
Coupled shear wall.
Approach A number of walls of varying heights (4 to 24 stories) and coupling ratios (0.25 to 0.6) are
designed using direct displacement design procedures outlined in Priestley et al. (2007) and
DBD12 (Sullivan et al., 2012). By employing capacity design principles, sufficient ductility is
provided at wall base regions and plastic hinges are allowed to be formed at wall bases only
ensuring the upper portions to behave elastically (Pauley and Priestley, 1992). Coupling beams are
designed as diagonally reinforced as they have superior performance in shear during cyclic load
over conventionally reinforced coupling beams (Pauley and Binney, 1974). SeismoStruct V7
software (Seismosoft, 2014) is used for non-linear modeling and analysis. Wall elements are
modeled as inelastic displacement based fiber-section frame element. Two diagonal truss elements
are used for modeling coupling beams. These elements are verified analytically comparing with
11
test results (Fox, 2014). Tangent stiffness proportional damping of 1% is
used at first mode of vibration. These coupled wall models are then
subjected to non-linear time history analysis for 10 number of design
spectrum compatible ground motion records.
Fig. 2. SeismoStruct model of coupled shear wall.
Results/Findings In this study, coupling ratios obtained from non-linear time history analysis results are compared
with the initially assumed coupling ratios for a range of building heights as shown in figures below.
(a) β = 0.25 (b) β = 0.4 (c) β = 0.5 (d) β = 0.6
Fig. 3. Coupling ratio comparison.
Followings are some conclusions that can be drawn from the above results.
1. Due to nonlinear effects during earthquakes, it is hard to obtain the expected coupling ratio
in reality. So, it is suggested to design for a bit larger coupling ratio than expected.
2. As the design coupling ratio increases, the difference in design and actual coupling ratio is
more pronounced.
3. Higher the number of stories, larger is the deviation of actual coupling ratio from the
designed one. This is due to the increase in wall moments due to higher mode effects in
high-rise buildings.
References: [1] M.J. Fox, “Seismic Design of Coupled Walls,” Master Thesis, ROSE Programme, UME School, IUSS Pavia, Italy,
2013.
[2] M.J.N. Priestley, G.M. Calvi and M.J. Kowalsky, “Displacement Based Seismic Design of Structures”, IUSS Press,
Pavia, Italy, 2007.
[3] Seismosoft, “SeismoStruct V7.0 – A computer program for static and dynamic nonlinear analysis of framed
structures,” 2014, available from http://www.seismosoft.com.
[4] T. Pauley and J.R. Binney, “Diagonally Reinforced Coupling Beams of Shear Walls,” Publication SP-42, American
Concrete Institute 1974, pp. 579-598.
[5] T.J. Sullivan, G.M. Calvi and M.J.N. Priestley (Editors), “A Model Code for Displacement Based Seismic Design of
Structures, DBD12”, IUSS Press, Pavia, Italy, 2012.
[6] T. Pauley and M.J.N. Priestley, “Seismic Design of Reinforced Concrete and Masonry Buildings,”
10 15 20 25 300
4
8
12
16
20
24
no
. o
f st
ori
es
coupling ratio (%)
analysis
design
25 30 35 40 450
4
8
12
16
20
24
no
. o
f st
ori
es
coupling ratio (%)
analysis
design
35 40 45 50 550
4
8
12
16
20
24
no
. o
f st
ori
es
coupling ratio (%)
analysis
design
40 45 50 55 60 650
4
8
12
16
20
24
no
. o
f st
ori
es
coupling ratio (%)
analysis
design
12
8th
NEAJ SymposiumonCurrent and Future Technologies
Tokyo, JapanJanuary25, 2015
DETERMINATION OF WATER QUALITY INDEX OF BAGMATI
RIVER
Ram Krishna REGMI*1, Binaya Kumar MISHRA
2, Pingping LUO
3, Asako
TOYOZUMI-KOJIMA4, Kensuke FUKUSHI
5, Kazuhiko TAKEMOTO
6 1, 2,3,4,6
Institute for the Advanced Study of Sustainability, United Nations University 5Integrated Research System for Sustainability Science, The University of Tokyo
*Email: [email protected]
Abstract Water Quality Index (WQI) is valuable and unique rating to depict the overall water quality status
in a single term that is helpful for the selection of appropriate treatment technique to meet the
concerned issues. This method appears to be more systematic and gives comparative evaluation of
the water quality of sampling stations. The present study intended to assess the water quality of the
Bagmati River in Kathmandu, Nepal. The method consists of computation of the WQI on the basis
of physical-chemical and biological quality parameters obtained from the different monitoring
stations of the river during October 2012 to September 2013. A comparative analysis revealed the
fact that there exists a significant difference in water quality between rural and urban areas. The
quality of river water is extremely poor and not suitable enough for the purpose of agriculture.
Keywords: Water Quality Index, Bagmati River, sampling stations, physical-chemical
parameters
13
8th
NEAJ Symposium on Current and Future Technologies
Tokyo, Japan January 25, 2015
DEVELOPMENT OF METHODOLOGY FOR LANDSLIDE AND
DEBRIS FLOW FORECASTING SYSTEM
Badri Bhakta SHRESTHA*1
1 International Centre for Water Hazard and Risk Management, Public Works Research Institute,
Tsukuba, Japan
* Email: [email protected]
Keywords: Landslide, debris flow, forecasting, snake curve, soil water index
Background Rainfall and soil water are important indicators of rainfall-induced landslide and debris flow. In this
paper, rainfall-based forecasting approach for landslide and debris flow has been presented. The
relationship between rainfall and soil water index (SWI) has been analyzed for forecasting system by
using hydrological distributed model. The soil water is an important parameter in the hydrological
balance and is essential for understanding land-surface interactions [1]. The approach has been
analyzed by using both ground-observed and satellite based rainfall data. The satellite based rainfall
data could also be useful to get supplementary information for forecasting system. The Sabagawa
river basin located in Yamaguchi prefecture of Japan was selected for case study. There was a
heavy rainfall in the Sabagawa river basin in July 2009 and large number of sediment disasters
occurred in the areas. The relationship between rainfall and soil water index was thus analyzed for
rainfall event in July 2009.
Approach The rainfall-runoff and temporal variation of
soil moisture in the soil mass were computed
by using Integrated Flood Analysis System
(IFAS) model. The IFAS is a concise
rainfall-runoff analysis system based on a
hydrological distributed tank model (Fig. 1)
[2]. In the model Global map elevation and
land cover data were used. The three layer
tanks (surface, subsurface and aquifer layers)
were considered. The model was calibrated
and validated by comparing simulated
discharge with observed discharge. The
rainfall event in July 2009 was used for
calibration of model and the calibrated
parameters were validated using rainfall
event in September 2005. The absolute value
of the soil water index was defined as the
sum of water depth in each of the tank layers.
The relationship between SWI and rainfall
was analyzed by using ground-observed
rainfall and satellite based rainfall data (3B42RT and GSMaP).
Fig. 1 Basic structure of a model
14
Results and Discussions Figure 2 shows comparison
of calculated river discharges
with observed discharges at
Manao station. The
calculated discharges using
ground rainfall and 3B42RT
satellite based rainfall data
are more agreeable with
observed discharges. Figure
3 shows the relationship of
rainfall and soil water index
calculated by using ground
rainfall and satellite based
rainfall data at Manao station.
The figures also show the
calculated snake line which
could be used for early
warning and forecasting
systems. The soil water index
increases when rainfall
intensity is increased, which
can cause sediment disasters
in the area. The satellite based
rainfall data also could be
useful to get supplementary
information for forecasting
and warning system of
sediment disasters. The results
show that results of SWI
obtained using 2B42RT
satellite based rainfall data are
closer to those obtained using
ground rainfall data than
GSMaP rainfall. The snake lines could be
useful for forecasting and
warning system of sediment
disasters. To use snake line for
warning system in sediment
disasters, critical lines for
warning criteria, alarm criteria and evacuation criteria should be determined based on past data of
sediment disasters. The determination of critical line is very important for judging warning criteria
based on snake line. The warning/alerting can be issued when snake line crosses the critical line. The
lines inside red circle in Fig. 3 (b) could be critical line for possibility of sediment disaster occurance.
References: [1] Hunt, E. D., Hubbard, K. G., Wilhite, D. A., Arkebauer, T. J. and Dutcher, A. L.: The development and
evaluation of a soil moisture index, International Journal of Climatology, Vol. 29, pp. 747-759, 2008.
[2] Sugiura, T., Fukami, K., Fujiwara, N., Hamaguchi, K., Nakamura, S., Hironaka, S., Nakamura, K., Wada,
T., Ishikawa, M., Shimizu, T., Inomata, H. and Ito, K.: Development of integrated flood analysis system
(IFAS) and its applications, Proceedings of 7th ISE & 8th HIC, Chile, 2009.
Figure 2 (a) Relationship between rainfall and soil water index, and (b) Calculated snake lines using ground
observed and satellite based rainfall data (at Manao Station).
0
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40
50
60
70
0
30
60
90
120
150
180
18-Jul 19-Jul 20-Jul 21-Jul 22-Jul
Rainfall-Ground
SWI-Ground
SWI-3B42RT
SWI-Gsmap-Ori
SWI-Gsmap-Cor
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r In
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infa
ll (
mm
)
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70
0 20 40 60 80 100 120 140 160 180
Ra
infa
ll (
mm
/hr)
Soil Water Index
SWI-Ground
SWI-3B42RT
SWI-Gsmap-Ori
SWI-Gsmap-CorSnake lines
Possibility of sediment
disaster occurrence
(b)
(a)
Fig. 3 (a) Relationship between rainfall and soil water index, and (b)
Calculated snake lines using ground observed and satellite based
rainfall data (at Manao Station).
0
20
40
60
80
1000
500
1000
1500
2000
2500
18-Jul 19-Jul 20-Jul 21-Jul 22-Jul 23-Jul
Rainfall Ground
Measured Discharge
Ground
Ori-Gsmap
Cor-GsMap
3B42RT
Date
Dis
cha
rge
(m3/s
ec)
Ra
infa
ll (
mm
)
Fig. 2 Calculated and observed discharge at Manao station
15
8th
NEAJ Symposium on Current and Future Technologies
Tokyo, JapanJanuary25, 2015
EXPERIMENTAL EVIDENCE OF IMPACT OF FLOW DIRECTION
ON DYKE BREACH CHARACTERISTICS DUE TO FLOW
OVERTOPPING
Pawan Kumar BHATTARAI*1, Hajime NAKAGAWA
2, Kenji KAWAIKE
3, Hao
ZHANG4
1, 2,3
Disaster Prevention Research Institute, Kyoto University 4 Natural Sciences Cluster Research Faculty, Kochi University
*Email: [email protected]
Keywords: Embankment, Dyke breach, Lateral widening, breach characteristics
Background
Dykes are among the most ancient and widely used defense structures against river flooding in the
world. In the context of this work, we refer to dykes as to man-made earthen embankments built
along a river parallel to the river flow and flow strikes the dike length in an angle but not
perpendicularly.Flooding from embanked rivers may occur when the structural defense fails in
containing the water flow inside the river banks.In the context of breach modeling, flood
embankment failure isconsidered to be the situation where erosion or structural failure of the
earthen embankment cause flood water to pass over or through the embankment in an increasingly
uncontrolled manner, leading to a hole or breach in the dyke. There is a distinct different in the
failure processes regarding dyke breach and dam breach process (differentiated mainly by flow
direction) which has to be considered when focusing on the breach characteristics analysis.Many
researchers tried to use the embankment breach model to dyke breach cases but that concept is not
right.Considering these facts, an extensive experimental study were done in Ujigawa Open
Laboratory, Disaster Prevention Research Institute, Kyoto University, Japan to compare the breach
characteristicsfor dyke and embankment breach cases with systematic variation of sediment sizes
forming dyke or embankment materials.. As the majority of dyke breaches are due to overtopping,
this is investigated in detail in the current research.
……………………………………………………………………………………………………….
Approach
Two different Experimental setups were developed considering the dyke breach and dam breach
cases so that proper comparison can be performed with dimensionless parameters.
Experiment for case 1 (Dam breach) The nine breach tests were performed in a Poly Vinyl Chloride (PVC) sided flume as the river and
the embankment were placed parallel to the river flow but since the embankment has also PVC
walls both sides; the flow direction to the embankment becomes perpendicular resembling the
embankment breach process. The details of the experimental setup are as shown in figure 1.
Experiment for case 2 (Dyke breach) Here, the trapezoidal river flume was prepared with an embankment in conjunction with river
side-slope so that flow river flow is parallel to the embankment; the flow were not perpendicular to
the embankment length; the length of embankment was increased by three times resembling the
realistic dyke model. The details of the experimental setup are as shown in figure 2.
All experiments were conducted using a constant flow discharge in a flume Qin, referred to as the
inflow, to obtain the simple boundary condition. The dyke material was initially provided with 5%
16
moisture content by weight and thoroughly mixed and then compacted with the help of a tamping
plate and cylindrical roller by spraying water layer by layer until about approx. 90% compaction
was achieved.
a) Plan View b) Cross section along X-X shown in a)
Fig.1 Experimental flume setup for Case 1 (Dam Breach)
……a) Plan View b) Cross section along Y-Y shown in (a)
Fig.2Experimental flume setup for Case 2 (Dyke breach)
Results/Findings
References: [1] Chinnarasri,C., Tingsanchali, T., Weesakul, S., Wongwises, S.(2003).”Flow patterns and damage of dike
overtopping.” Int. J. Sediment Res. 18(4), 301–309.
[2[ Bhattarai, P.K., Nakagawa, H., Kawaike K. and Zhang H. (2014) “Experimental Study on River Dyke breach
Characteristics Due to Overtopping Flow”,Journal of Japanese Society of Natural Disaster Science,Vol.33, 2014
17
Publication of Nepalese Engineers Association, Japan (NEAJ)
http://www.neajc.org/
Email: [email protected]